Yog Sothoth's bad reputation comes mostly from a story about one of his mortal descendants, who's family were heavily mutated and incredibly foul.
lovecraft.fandom.com
lovecraft.fandom.com

Wilbur Whateley
Wilbur Whateley is a fictional character created by H. P. Lovecraft for his short story "The Dunwich Horror". In the rural town of Dunwich, Massachusetts on February 2, 1913 at 5 a.m., Lavinia Whateley gave birth to a son named Wilbur Whateley. The date of his birth is noted for the night before...

Dunwich Horror (being)
The Dunwich Horror is a fictional entity created by H. P. Lovecraft for his eponymous short story. The Dunwich Horror is the inhuman child of Lavinia Whateley and Yog-Sothoth, who was conceived to free the Great Old Ones so that they may reclaim the Earth. Its existence was kept secret by its...